1. Field of the Invention
The present general inventive concept relates to a spoke-processing apparatus and a method usable with sequential color display devices. More particularly, the present general inventive concept relates to a spoke-processing apparatus and a method usable with sequential color display devices which use spokes depending on an extent of a color saturation and a luminance of a color signal.
2. Description of the Related Art
A spoke on a color wheel refers to a region between a location where the beam spot hits a boundary of a current color segment of the color wheel and a location where the beam spot hits a boundary of the next color segment. That is, the spoke is a transition area between neighboring color segments of the color wheel in which the colors of the neighboring segments are blended.
U.S. Pat. No. 6,324,006B1 discloses spokes and re-capturing of light emitted in spoke areas in a sequential color imaging system. More specifically, the U.S. Pat. No. 6,324,006B1 discloses an image-forming method comprising steps of: sequentially emitting color signals to pass through at least two single-colored segments and at least one spoke area, converting the color signal that passes through the spoke area into composite color data, and focusing each converted signal to form multi-colored images. The U.S. Pat. No. 6,324,006B1 provides an improvement of image brightness that can be achieved by using the spoke areas in the color wheel-driven display device.
FIG. 1A is a block diagram illustrating a conventional color display device using spokes in a color wheel.
As illustrated in FIG. 1A, the conventional color display device has an 8-bit RGBW processor 110, a RGBW split bit generator 120, a white-level sensor 130, a spoke bit generator 140, and a digital micro-mirror device(DMD) format converter 150.
As illustrated in FIG. 1A, the 8-bit RGBW processor 110 splits a 24-bit RGB input signal into a 24-bit red (R), green (G), and blue (B) color signal and an 8-bit white (W) color signal. The RGBW split bit generator 120 converts the red, green, and blue color signal and the white color signal received from the 8-bit RGBW processor 110 into a 48-bit RGBW including split-bits (i.e., 48 bit white) to drive the digital micro-mirror device (DMD). The white-level sensor 130 divides gray levels that are higher than a gray level of 144 (out of gray levels 0 to 255) into 16 gray levels (e.g., 144, 151, 158, etc.), and detects the 16 gray levels. In particular, the white level sensor 130 detects one of the 16 gray levels as a gray level of the 8-bit white color signal received from the 8-bit RGBW processor 110.
The spoke bit generator 140 calculates an amount of white color to be added to an input color signal according to the detected gray level of the 8-bit white color signal. That is, assuming that the white color results when all lights from the spokes Srw—spokes between red and white color segments, Swg—spokes between white and green color segments, Sgb—spokes between green and blue color segments, and Sbr—spokes between blue and red color segments are mixed, the spoke bit generator 140 calculates the amount of the white color to be added to the input color signal. The DMD format converter 150 uses the amount of the white color calculated by the spoke bit generator 140 to be added to the input color signal and the split 48-bit RGBW signal for format conversion necessary to drive the DMD.
FIG. 1B is a view illustrating a comparison between a luminance of output images when the spoke areas are used (i.e., turned on) and when the spoke areas are not used (i.e., turned off).
As illustrated in FIG. 1B, line A represents an input-to-output luminance when the spoke areas are not used, and line B represents an input-to-output luminance when the spoke areas are used.
FIG. 1B illustrates that the luminance is increased when the spoke areas are used, compared to when the spoke areas are not used. As mentioned above, the luminance of the input color signal can be improved when the spoke areas are used as compared to when the spoke areas are not used. However, an expansion of color ranges is relatively limited since the spoke areas are only applied to a luminance range.
Further, if the white color is added to the input color signal, the line B causes an image signal to be nonlinear including 16 steps starting from the gray level 144, since when a gray level of the input color signal is higher than a predetermined gray level (i.e., the gray level 144), the gray level of the input color signal is divided into 16 gray levels and the white color is only added to the 16 gray levels. The images processed by the conventional color display device using the spokes in a color wheel can occasionally have distorted colors as well as a color imbalance.